Acute myeloid leukemia (AML) is the most common form of adult acute leukemia with 5 year survival rates of ˜5% and ˜30% for elder and younger patients, respectively1-5. Although >70% of AML patients achieve an initial remission with induction chemotherapy, chemotherapy-resistant leukemia cells ultimately cause relapse in most patients3,4,6. Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a potentially curative treatment for chemotherapy-resistant AML7-9. However, transplantation has toxicities restricting its use in older and debilitated patients. Moreover, although allogeneic immune cells can kill leukemic cells10-14, they commonly also recognize allo-antigens expressed on normal cells and tissues inducing severe, and sometimes lethal graft-versus-host-disease (GvHD)14-16. In addition, limited donor availability prevents wide use of allo-HSCT. Hence, development of safer and more effective cell-based therapies for AML is needed.
Double negative T cells (DNTs) are mature peripheral lymphocytes that express the CD3-T cell receptor (TCR) complex, including both αβ- and γδ-TCR, but do not express CD4 and CD8, and are not iNKT cells (FIG. 1b). DNTs represent 1-3% of peripheral blood mononuclear cells (PBMCs)17. Previously, we have shown that mouse DNTs could rescue mice from a lethal dose of lymphoma cells and DNTs expanded from AML patients were cytotoxic to autologous AML cells in vitro17,18. While we showed that DNTs expressing αβ- and γδ-TCR have comparable level of cytotoxicity17, the mechanisms by which DNTs mediate their anti-leukemia activity remain unclear and no data exists regarding the in vivo anti-leukemic potential of these immune effectors. Further, it remains unknown whether DNTs expanded from healthy donors (HDs) can target AML cells while sparing non-malignant hematological cells of the donor from which they were derived.